Swift JSON 使用字典数组解析字典

Question

我是使用 Swift 语言进行 iOS 开发的初学者。我有一个 JSON 文件包含如下数据。

{
    "success": true,
    "data": [
             {
                 "type": 0,
                 "name": "Money Extension",
                 "bal": "72 $",
                 "Name": "LK_Mor",
                 "code": "LK_Mor",
                 "class": "0",
                 "withdraw": "300 $",
                 "initval": "1000 $"
             },
             {

             },
             {

             },
             ]
}

我想解析这个文件并且必须 return 包含 JSON 文件中数据的字典。这是我写的方法。

enum JSONError: String, ErrorType {
    case NoData = "ERROR: no data"
    case ConversionFailed = "ERROR: conversion from JSON failed"
}

func jsonParserForDataUsage(urlForData:String)->NSDictionary{
    var dicOfParsedData :NSDictionary!
    print("json parser activated")
    let urlPath = urlForData
    let endpoint = NSURL(string: urlPath)
    let request = NSMutableURLRequest(URL:endpoint!)
            NSURLSession.sharedSession().dataTaskWithRequest(request) { (data, response, error) -> Void in
                do {

                    guard let dat = data else {
                        throw JSONError.NoData
                    }
                    guard let dictionary: NSDictionary = try NSJSONSerialization.JSONObjectWithData(dat, options:.AllowFragments) as? NSDictionary else {
                        throw JSONError.ConversionFailed
                    }

                    print(dictionary)
                    dicOfParsedData = dictionary

                } catch let error as JSONError {
                    print(error.rawValue)
                } catch {
                    print(error)
                }
                }.resume()

          return dicOfParsedData

}

当我将此方法修改为 return 字典时，它总是 return nil。我该如何修改这个方法。

Answer 1

您不能 return 异步任务。您必须改用回调。

添加这样的回调：

completion: (dictionary: NSDictionary) -> Void

到您的解析器方法签名：

func jsonParserForDataUsage(urlForData: String, completion: (dictionary: NSDictionary) -> Void)

并在您想要 "return" 的数据可用的地方调用完成：

func jsonParserForDataUsage(urlForData: String, completion: (dictionary: NSDictionary) -> Void) {
    print("json parser activated")
    let urlPath = urlForData
    guard let endpoint = NSURL(string: urlPath) else {
        return
    }
    let request = NSMutableURLRequest(URL:endpoint)
    NSURLSession.sharedSession().dataTaskWithRequest(request) { (data, response, error) -> Void in
        do {

            guard let dat = data else {
                throw JSONError.NoData
            }
            guard let dictionary = try NSJSONSerialization.JSONObjectWithData(dat, options:.AllowFragments) as? NSDictionary else {
                throw JSONError.ConversionFailed
            }

            completion(dictionary: dictionary)

        } catch let error as JSONError {
            print(error.rawValue)
        } catch let error as NSError {
            print(error.debugDescription)
        }
    }.resume()

}

现在您可以使用此方法和尾随闭包来获取 "returned" 值：

jsonParserForDataUsage("http...") { (dictionary) in
    print(dictionary)
}

Swift JSON 使用字典数组解析字典

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